Internal shock absorber plunger

ABSTRACT

An improved plunger mechanism apparatus has an internal shock absorber to increase plunger life and increases life of components found at a top and well bottom. The internal shock absorber can be an elastomer spring, die coil spring or wave spring. An actuator rod within the plunger hits the bottom of the well and compresses the internal spring, absorbing all or part of the impact shock. Likewise, when a plunger rises to the well top with a high velocity, damage is avoided as the top of the plunger hits well top apparatus. Reduction in well bottom bumper spring collapses, spring damage, and plunger damage is obtained. Damage to well bottoms having no bumper springs is avoided. Efficiency of well flow is increased by the increase in the reliability of the well operation.

FIELD OF THE INVENTION

The present invention relates to an improved plunger lift apparatus for the lifting of formation liquids in a hydrocarbon well. More specifically the improved plunger consists of an internal shock absorber plunger apparatus that operates to allow a longer life via an internal spring design to absorb shock during plunger falls to a well bottom, and high velocity rises to the well top.

BACKGROUND OF THE INVENTION

A plunger lift is an apparatus that is used to increase the productivity of oil and gas wells. Nearly all wells produce liquids. In the early stages of a well's life, liquid loading is usually not a problem. When rates are high, the well liquids are carried out of the well tubing by the high velocity gas. As the well declines, a critical velocity is reached below which the heavier liquids do not make it to the surface and start to fall back to the bottom exerting back pressure on the formation, thus loading up the well. A basic plunger system is a method of unloading gas in high ratio oil wells without interrupting production. In operation, the plunger travels to the bottom of the well where the loading fluid is picked up by the plunger and is brought to the surface removing all liquids in the tubing. The plunger also keeps the tubing free of paraffin, salt or scale build-up. A plunger lift system works by cycling a well open and closed. During the open time a plunger interfaces between a liquid slug and gas. The gas below the plunger will push the plunger and liquid to the surface. This removal of the liquid from the tubing bore allows an additional volume of gas to flow from a producing well. A plunger lift requires sufficient gas presence within the well to be functional in driving the system. Oil wells making no gas are thus not plunger lift candidates.

A typical installation plunger lift system 100 can be seen in FIG. 1. Lubricator assembly 10 is one of the most important components of plunger system 100. Lubricator assembly 10 includes cap 1, integral top bumper spring 2, striking pad 3, and extracting rod 4. Extracting rod 4 may or may not be employed depending on the plunger type. Contained within lubricator 10 is plunger auto catching device 5 and plunger sensing device 6. Sensing device 6 sends a signal to surface controller 15 upon plunger 200 arrival at the well top. Plunger 200 can represent the plunger of the present invention or other prior art plungers. Sensing the plunger is used as a programming input to achieve the desired well production, flow times and wellhead operating pressures. Master valve 7 should be sized correctly for the tubing 9 and plunger 200. An incorrectly sized master valve 7 will not allow plunger 200 to pass through. Master valve 7 should incorporate a full bore opening equal to the tubing 9 size. An oversized valve will allow gas to bypass the plunger causing it to stall in the valve. If the plunger is to be used in a well with relatively high formation pressures, care must be taken to balance tubing 9 size with the casing 8 size. The bottom of a well is typically equipped with a seating nipple/tubing stop 12. Spring standing valve/bottom hole bumper assembly 11 is located near the tubing bottom. The bumper spring is located above the standing valve and can be manufactured as an integral part of the standing valve or as a separate component of the plunger system. It is designed to protect the tubing from plunger impact in the absence of fluid. Fluid 17 would accumulate on top of plunger 200 to be carried to the well top by plunger 200.

Surface control equipment usually consists of motor valve(s) 14, sensors 6, pressure recorders 16, etc., and an electronic controller 15 which opens and closes the well at the surface. Well flow ‘F’ proceeds downstream when surface controller 15 opens well head flow valves. Controllers operate on time, or pressure, to open or close the surface valves based on operator-determined requirements for production. Modern electronic controllers incorporate features that are user friendly, easy to program, addressing the shortcomings of mechanical controllers and early electronic controllers. Additional features include: battery life extension through solar panel recharging, computer memory program retention in the event of battery failure and built-in lightning protection. For complex operating conditions, controllers can be purchased that have multiple valve capability to fully automate the production process.

FIG. 2 is a side view of the upper sections of various plunger sidewall geometries existing with prior art elements from element 41 and upward. All geometries described are solid plungers and all can be found in present industrial offerings. Similar geometries also exist and will have internal orifices. The aforementioned sidewall geometries are described as follows:

-   -   A. Solid ring 22 sidewall geometry is shown in solid plunger         mandrel 20. Solid sidewall rings 22 can be made of various         materials such as steel, poly materials, Teflon®, stainless         steel, etc. Inner cut groves 30 allow sidewall debris to         accumulate when a plunger is rising or falling.     -   B. Shifting ring plunger mandrel 80 is shown with shifting ring         81 sidewall geometry. Shifting rings 81 sidewall geometry allow         for continuous contact against the tubing to produce an         effective seal with wiping action to ensure that all scale, salt         or paraffin is removed from the tubing wall. Shifting rings 81         are all individually separated at each upper surface and lower         surface by air gap 82.     -   C. Pad plunger mandrel 60 has spring-loaded interlocking pads 61         in one or more sections. Interlocking pads 61 expand and         contract to compensate for any irregularities in the tubing,         thus creating a tight friction seal.     -   D. Brush plunger mandrel 70 incorporates a spiral-wound,         flexible nylon brush 71 surface to create a seal and allow the         plunger to travel despite the presence of sand, coal fines,         tubing irregularities, etc.     -   E. Flexible plungers (not shown) are flexible for coiled tubing         and directional holes, and can be used as well in straight         standard tubing.

All aforementioned upper sections have a top collar shown with a standard American Petroleum Institute (API) internal fishing neck ‘A’ (see FIG. 3) and added to any of the above-described geometries. The upper section has upper end sleeve 41 with upper threaded male section 42 used to attach various bottom ends, which will be described below. If retrieval is required, a spring loaded ball within a retriever and protruding outside its surface would thus fall within the API internal fishing neck at the top of the plunger, wherein the inside diameter of the orifice would increase to allow the ball to spring outward. This condition would allow retrieving of the plunger if, and when, necessary.

Recent practices toward slim-hole wells that utilize coiled tubing also lend themselves to plunger systems. Because of the small tubing diameters, a relatively small amount of liquid may cause a well to load-up, or a relatively small amount of paraffin may plug the tubing.

Plungers use the volume of gas stored in the casing and the formation during the shut-in time to push the liquid load and plunger to the surface when the motor valve opens the well to the sales line or to the atmosphere. To operate a plunger installation, only the pressure and gas volume in the tubing/casing annulus is usually considered as the source of energy for bringing the liquid load and plunger to the surface.

The major forces acting on the cross-sectional area of the bottom of the plunger are:

-   -   The pressure of the gas in the casing pushes up on the liquid         load and the plunger.     -   The sales line operating pressure and atmospheric pressure push         down on the plunger.     -   The weight of the liquid and the plunger weight pushes down on         the plunger.     -   Once the plunger begins moving to the surface, friction between         the tubing and the liquid load acts to oppose the plunger.     -   In addition, friction between the gas and tubing acts to slow         the expansion of the gas.

In certain wells, a plunger will fall towards the well bottom at a relatively high velocity. This high velocity will result in an impact force at the well bottom that must be absorbed entirely by the plunger and bottom of a well seating nipple/tubing stop 12 and spring standing valve/bottom hole bumper assembly 11 (FIG. 1). High velocity leads to greater impact force and can result in damage to the plunger, and/or the spring standing valve/bottom hole bumper assembly. Prior art designs have utilized plungers with externally located springs to help absorb the energy generated by the plunger force hitting the well bottom. Some wells do not have a bumper spring at the bottom and the impact is entirely absorbed by the plunger itself! If a bumper spring does exist, it can collapse over time due to the repeated stress of the impact forces on it. Also, plunger damage can occur causing the need to replace plungers more frequently. In many occasions a plunger will also rise at a high velocity from the well bottom to the well top. This can occur when liquid levels are low or when an operator allows the plunger to lift prior to proper liquid loading. A high velocity rise causes damage to the aforementioned well top apparatus and to the plunger itself. This problem will increase well maintenance cost. Prior art does not address this problem.

A prior solution is shown in FIG. 3, which shows prior art pad plunger mandrel 60 geometry (see FIG. 2) with a fishing neck top section A, and the addition of an external bottom spring 32 attached via weld 31. The prior art solution with such an external spring, acting as a shock absorber, tends add reliability problems to both the plunger and well bottom assembly. It can result in failures with weld and/or spring and also places more wear and tear on the well bottom seating nipple/tubing stop and spring standing valve/bottom hole bumper assembly.

What is needed is a plunger lift apparatus with a more reliable shock absorber, one that provides the ability of the well bottom to be less restrictive and one that will eliminate damage to well top apparatus when a high velocity plunger rise occurs. The apparatus of the present invention provides a solution to these problems.

SUMMARY OF THE INVENTION

The main aspect of the present invention is to provide an internal shock absorber plunger apparatus in a high liquid well when plunger falling velocity produces a large impact force at the well bottom.

Another aspect of the present invention is to provide an internal shock absorber plunger apparatus that will protect the well top apparatus and the plunger when a high velocity plunger rise occurs.

Another aspect of the present invention is to provide a spring within the plunger to function as the shock absorbing body.

Another aspect of the present invention is to provide for less restriction on a well bottom.

Another aspect of the present invention is to provide a shock absorber plunger that will increase reliability levels.

Another aspect of the present invention is to provide a shock absorber plunger that will efficiently force fall Inside the tubing to the well-hole bottom with increased speed without impeding plunger or well bottom damage.

Another aspect of the present invention is to provide a shock absorber plunger that can be used with any existing plunger sidewall geometry.

Another aspect of the present invention is to allow for a shock absorber plunger that can be easily manufactured.

Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

The present invention is an improved plunger mechanism apparatus having an internal shock absorber to increase plunger life as well as to increase life of components found at a well bottom. The internal shock absorber can be an elastomer spring, die coil spring or wave spring. An actuator rod within the plunger hits the bottom of the well and compresses the internal spring, which absorbs all or part of the impact shock. The plunger's descent rate in certain wells will result in an impact force that can be absorbed by the plunger itself. A high velocity plunger rise will also result in an impact force at the well top that can be absorbed by the plunger itself.

The present invention comprises a plunger lift apparatus consisting of a top section, which is typically a standard American Petroleum Institute (API) fishing neck, or other designs; a solid core mid section allowing for various aforementioned sidewall geometries; and a lower internal shock absorber section. The lower internal shock absorber section can be designed in various ways but will basically consist of an actuator rod, a captive actuator and an internal spring. The internal spring can be a wave spring, a die coil spring, or an elastomer-type spring (i.e. Viton®, etc.), which offers excellent resistance to aggressive fuels and chemicals. One of the additional embodiments of the present invention will incorporate dual shock absorber sections, that is a shock absorbing element at each end section, one at the top and one at the bottom of the plunger. Yet another additional embodiment will incorporate a mid-section shock absorber element.

The internal shock absorber plunger of the present invention allows for improved reliability in wells that have high velocity with respect to falling plungers. It allows for less restriction at the well bottom, high reliability, ease of manufacture, and incorporation of the design into existing plunger geometries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (prior art) is an overview depiction of a typical plunger lift system installation

FIG. 2 (prior art) is a side view of the upper section of various sidewall geometries of well plungers.

FIG. 3 (prior art) is a side view of pad plunger geometry with an externally attached spring.

FIG. 4 is a side cross-sectional view of the lower section of the internal shock absorber plunger of the preferred embodiment of the present invention using a standard die coil spring.

FIG. 5 is an isometric exploded view of bottom section of the internal shock absorber plunger of the preferred embodiment of the present invention.

FIG. 6 is a side cross-sectional view of the lower section of the internal shock absorber plunger of an alternate embodiment of the present invention using a standard die coil spring.

FIG. 7 is an isometric exploded view of bottom section of the internal shock absorber plunger of an alternate embodiment of the present invention.

FIG. 8 is a side view of the internal shock absorber plunger utilized with various sidewall geometries.

FIG. 9 is a side view of the central section of various well plungers for a dual internal shock absorber second embodiment of the present invention showing existing prior art sidewall geometries.

FIG. 10 is a side cross-sectional view the preferred embodiment of the upper assembly for the dual internal shock absorber.

FIG. 11 is an isometric exploded view of the upper shock absorbing assembly for the dual internal shock absorber.

FIG. 12 is a side cross-sectional view of an alternate embodiment of the upper assembly for the dual internal shock absorber plunger.

FIG. 13 is an isometric exploded view of an alternate embodiment of the upper assembly for the dual internal shock absorber plunger.

FIG. 14 is side view, including a mid-section cross-sectional view, for a mid-section internal shock absorber plunger third embodiment of the present invention.

FIG. 15 is an isometric exploded view of the casing assembly of mid-section internal shock absorber plunger third embodiment of the present invention.

Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the present invention provides an internal shock absorber plunger apparatus that will improve productivity levels in high liquid wells when plunger falling velocity produces a large impact force at the well bottom that contains a bumper spring or that does not contain a bumper spring. The present invention will also protect the plunger and the apparatus at the well top in the case of a high velocity lift. A high velocity lift will occur in low liquid wells, as well as instances when an operator will cycle the plunger prior to liquid loading.

FIG. 4 shows the bottom removable assembly 300 of the internal shock absorber plunger containing the internal shock absorber for the preferred embodiment of the present invention. Lower removable assembly 300 is the major element of the present invention and can be added to any aforementioned geometric upper section. Lower removable assembly 300 consists of actuator rod (piston) 36 having external thread interface 52A, captive nut (cap) 35 having external thread interface 54A, shock absorbing elastomer spring 49, seal nut 34 having internal thread interface 52B, and case housing (cylinder wall) 33 having internal thread interface 54B at its lower end, also having an inner lower ledge to contain the upper end of shock absorbing elastomer spring 49. To mate with upper sections (ref. FIG. 2), case housing 33 has internal cavity 57 for accepting upper end sleeve 41. Upper threaded male section 42 (ref. FIG. 2) is received by threaded female section 56. It should also be noted that shock absorbing elastomer spring 49 could be replaced with shock absorbing die coil spring 48 (see FIG. 7) or with shock absorbing wave type spring 47 (see FIG. 7). Shock absorbing elastomer spring 49 can be Viton® or any other type elastomer. Material selections can be tuned to well conditions such as temperature, falling/rising distance, resistance to fuels or chemicals present in the fluid, etc. The present invention is not limited by the type of or by the design of the internal spring. Also spanner holes (not shown) could be easily added to parts such as seal nut 34, captive nut 35, and other parts as required, to aid in fastening.

The following steps are used to describe a basic sub-assembly of lower removable assembly 300:

-   -   a) Place shock absorbing elastomer spring 49 into case housing         33;     -   b) Slip captive nut (cap) 35 over actuator rod 36;     -   c) Screw seal nut 34 onto actuator rod 36 via thread interface         52;     -   d) Slide actuator rod 36 with attached seal nut 34 and with         captive nut 35 into case housing 33;     -   e) Screw captive nut 35 into case housing at thread interface 54         to complete removable assembly 300.     -   f) Screw lower removable assembly 300 into an upper section         (ref. FIG. 2) via placing internal cavity 57 onto upper end         sleeve 41 and screwing threaded female section 56 to upper         threaded male section 42.

When the plunger falls to the well bottom, actuator rod 36 will hit the aforementioned seating bumper spring assembly that is located near the tubing bottom. If a bumper spring does not exist, the plunger will hit a hard stop at the well bottom. Both the bumper spring assembly and the internal shock absorber plunger of the present invention will absorb the force generated by the impact. If a bumper spring does not exist, the entire impact force will be absorbed by the internal shock absorber. Upon impact, actuator rod 36 will move in direction ‘R’ and into shock absorbing elastomer spring 49 which will absorb a portion (or all) of the impact force. The ability the plunger to self-absorb shock at the well bottom will thus increase reliability levels. It will reduce the probability of bumper spring collapses, reduce damage to the plunger itself, and reduce damage to the well bottom itself. It also provides the ability to have less restriction at the well bottom, that is, elimination of the need for bumper spring assemblies at the well bottom. Thus the internal shock absorber plunger will efficiently force fall inside the tubing to the well-hole bottom without impeding plunger or well bottom damage. If the plunger rises with a high velocity, the present invention provides an internal plunger shock absorption as the plunger top hits a top striking pad or other well top apparatus.

FIG. 5 is an isometric exploded view of lower removable assembly 300 of the internal shock absorber plunger of an alternate embodiment of the present invention. It shows the basic five parts of lower removable assembly 300; actuator rod 36 has anvil B design with anvil groove 64 at one end has external thread interface 52A at its other end, captive nut 35 with external thread interface 54A, seal nut 34 with inner thread interface 52B, shock absorbing elastomer spring 49, and case housing 33. Access external hole 62A is for tightening lower removable assembly 300 to the upper section onto upper threaded male section 42. It should be noted that anvil B design could easily be replaced with other end type designs.

All parts are easy to manufacture and easy to assemble. Assembly to upper sections is completed via threaded female section 56.

FIG. 6 is an alternate embodiment of the present invention showing alternate lower removable assembly 400 of the internal shock absorber plunger containing the internal shock absorber. Lower removable assembly 400 is an alternate design to lower removable assembly 300 shown in FIGS. 4, 5. Alternate lower removable assembly 400 can be added to any aforementioned geometric top section in the same manner as previously described herein. Alternate lower removable assembly 400 consists of actuator rod (piston) 44, shock absorbing die coil spring 48, case housing (cylinder wall) 46 with internal female housing threaded area 51B, and lock nut 45 which has internal female threaded area 53 for accepting an upper threaded male section 42, and external male threaded section 51A for mating with housing 46 via internal female housing threaded area 51B. Grip holes 39 in lock nut 45 are used to grasp and mechanically tighten lock nut 45. Actuator rod 44 has an outer flange at its upper surface to hold it within case housing 46, which has an inner flange surface on its bottom side to hold actuator rod 44 within. Shock absorbing die coil spring 48 can also be replaced with shock absorbing wave spring 47 or with shock absorbing elastomer-type spring 49. The present invention is not limited by the spring type or by the spring design.

When the plunger falls to the well bottom, actuator rod 44 will hit seating bumper spring assembly or hit a hard stop at the well bottom. Upon impact, actuator rod 44 will move in direction ‘R’ and into shock absorbing coil spring 48 which will absorb a portion (or all) of the impact force. Likewise, when a plunger rises to the well top with a high velocity, damage is avoided as the top of the plunger hits well top apparatus and the internal shock absorbing coil spring 48 will absorb a portion (or all) of the impact force.

FIG. 7 is an isometric blow-up view of lower removable assembly 400 of the internal shock absorber plunger of an alternate embodiment of the present invention. Lower removable assembly 400 consists of actuator rod (piston) 44, die coil spring 48, case housing 46, and lock nut (threaded cap) 45 with internal female threaded area 53 for accepting upper threaded male section 42 (ref. FIG. 2), and outside male threaded area 51A for mating with housing 46 which has internal female housing threaded area 51B. Grip holes 39 are used to grasp and mechanically tighten lock nut 45. As previously discussed, shock absorbing die coil type spring 48 can also be replaced with shock absorbing wave spring 47 or with an elastomer-type spring 49. Access external hole 62B is for tightening lower removable assembly 400 to the upper section onto upper threaded male section 42.

Viewing FIG. 7 it can be seen that this alternate embodiment of the present invention basically consists of four parts in lower removable assembly 400; actuator rod 44, shock absorbing die coil spring 48, case housing 46 with internal female housing threaded area 51B, and lock nut 45 with inside female threaded area 53 for accepting upper threaded male section 42 (ref. FIG. 2), and outside male threaded area 51A for mating with inner female threaded area 51B on case housing 46. As previously discussed, shock absorbing die coil type spring 48 can also be replaced with shock absorbing wave spring 47 or with shock absorbing elastomer-type spring 49. All parts are easy to manufacture and easy to assemble. Assembly to upper sections is also via a simple thread at threaded interfaces 51, 53.

It should be noted that although both removable assemblies have been shown with upper female type receptacles and upper plunger sections have been shown with lower male type sections for joining each other, other designs could easily be employed to have removable assemblies with male upper sections and female upper plunger sections with female lower sections for mating.

FIG. 8 is a side view of the internal shock absorber plunger utilized with various sidewall geometries (including but not limited to mandrel geometries 20, 60, 70, 80). For illustrative purposes, aforementioned preferred embodiment lower removable assembly 300 is shown with solid plunger mandrel geometry 20 and shifting ring plunger mandrel geometry 80. Alternate embodiment lower removable assembly 400 is shown with pad plunder mandrel geometry 60 and brush plunger mandrel geometry 70. It should be noted that the present invention is not limited to any specific sidewall geometry and that any sidewall geometry can be used.

Although any top geometry can readily be used with the present invention, a standard American Petroleum Institute (API) internal fishing neck top is shown in FIG. 8.

A second embodiment of the present invention is an dual internal shock absorber and is shown in FIGS. 9, 10, 11, 12, 13 described below. In certain wells, the rising velocity can be several times faster than a falling velocity due to well pressure conditions. This second embodiment provides for ‘dual’ shock absorbing sections by adding a second shock absorbing ‘upper’ assembly. The shock absorbing upper assembly allows for improved internal shock absorption as needed based on well conditions.

FIG. 9 is a side view of the mandrel central section of various well plungers for a dual internal shock absorber second embodiment of the present invention showing existing prior art sidewall mandrel geometries between sleeves 41. As compared to aforementioned FIG. 2, additional upper end sleeve 41 and additional upper threaded male section 42 are added for accepting an additional upper end shock absorber assembly. All geometries depicted can be found in present industrial offerings. Similar geometries also exist and will have internal orifices. FIGS. 10, 11 as described below, depict the additional shock absorbing section that is added to upper sleeve 41 via screwing onto upper threaded male section 42. Each mandrel central section is symmetrically designed to hold both an upper shock absorbing assembly 300A or 400A (FIGS. 10, 11, 12, 13) and a lower shock absorbing assembly 300 or 400 (FIGS. 4, 5, 6, 7).

FIG. 10 is a side cross-sectional view the preferred embodiment for removable upper shock absorbing assembly 300A for the dual internal shock absorber using an elastomeric spring 49. Elastomeric spring 49 can be replaced with other type springs such as a wave spring or a die coil spring. All elements of FIG. 10 are exactly as described in FIG. 4 with the exception that actuator rod 36A has aforementioned fishing neck A design. Upper shock absorbing assembly 300A mates with central section (ref. FIG. 9) via internal cavity 57 for accepting upper end sleeve 41 and upper threaded male section 42 is received by threaded female section 56. Thus, adding upper assembly 300A adds a second shock absorbing assembly forming an dual internal shock absorbing plunger.

FIG. 11 is an isometric exploded view of the upper shock absorbing assembly 300A for the dual internal shock absorber. All parts of removable assembly 300A are as previously described in FIG. 5 above with the exception that actuator rod 36A has fishing neck A design for retrieval purposes.

FIG. 12 is a side cross-sectional view of an alternate embodiment of upper assembly 400A for the dual internal shock absorber plunger. Upper assembly 400A is an alternate design to upper assembly 300A shown in FIG. 10. All elements of FIG. 12 are exactly as described in FIG. 6 with the exception that actuator rod 44A has fishing neck A design. Upper shock absorbing assembly 400A mates with central section (ref. FIG. 9) via internal threads 53 for accepting upper threaded male section 42 (FIG. 9). Thus, adding upper assembly 400A adds a second shock absorbing assembly forming an dual internal shock absorbing plunger.

FIG. 13 is an isometric exploded view of an alternate embodiment of upper assembly 400A for the dual internal shock absorber plunger. All parts of removable assembly 400A are as previously described in FIG. 7 above with the exception that actuator rod 44A has fishing neck A design for retrieval purposes.

FIG. 14 is side view, including a mid-section cross-sectional view, for a mid-section internal shock absorber plunger 500 third embodiment of the present invention. For a rising plunger condition, upper mandrel 502 will hit the well top and for a falling plunger condition, lower mandrel 504 will hit the well bottom. In either case elastomer spring 49 will absorb some or all of the impact energy. Casing assembly 506 contains mid-section casing 66 having threaded interfaces at either ends, one internal elastomer spring 49, two captive nuts 34 for attaching upper mandrel 502 and lower mandrel 504, and two captive nuts 35 for containing both mandrels. Shock absorbing elastomer spring 49 could be replaced with shock absorbing die coil spring 48 (see FIG. 7) or with shock absorbing wave type spring 47 (see FIG. 7). Upper mandrel 502 at it upper end has a fishing neck A design, while lower mandrel 504 is an anvil B end design as previously shown in FIGS. 4, 5, 8. Mandrels are shown with aforementioned shifting ring geometry having shifting rings 81, which are all individually separated at each upper surface and lower surface by air gap 82. It should be noted that although a shifting ring geometry is shown, other previously described sidewall geometries could also be used.

FIG. 15 is an isometric exploded view of casing assembly 506 of mid-section internal shock absorber plunger third embodiment of the present invention. Assembly of mandrels to casing assembly is as follows:

-   -   a) Slide upper mandrel 502 thru upper captive nut 35 and thread         upper seal nut 34 onto it via seal nut threads 52B mating to         upper mandrel threads 52C.     -   b) Slide lower mandrel 504 thru lower captive nut 35 and thread         lower seal nut 34 onto it via seal nut threads 52B mating to         lower mandrel threads 52D.     -   c) Place elastomer spring 49 into casing 66.     -   d) Thread upper captive nut 35 via threads 54A onto casing 66         via upper casing threads 54C, thereby securing upper mandrel 502         to casing 66.     -   e) Thread lower captive nut 35 via threads 54A onto casing 66         via lower casing threads 54C (not shown), thereby securing lower         mandrel 504 to casing 66, thus completing assembly of the         mid-section internal shock absorber plunger third embodiment of         the present invention.

The present invention optimizes well efficiency and reliability due to the fact that it has an internal shock absorber to allow it to quickly travel to the well bottom, or to quickly travel to the well top, without causing damage. This results in the ability to provide fewer restrictions at the well bottom and avoids damage to the apparatus at a well top, as well as avoiding to the plunger itself. The present invention provides an improved plunger mechanism apparatus having an internal shock absorber to increase plunger life as well as to increase life of components found at a well top and well bottom. The internal shock absorber can be an elastomer spring, die coil spring or wave spring, which absorbs all or part of the impact shock. The plunger's descent rate in certain wells will result in an impact force that can be partially, or fully, absorbed by the plunger itself. Likewise, a fast ascent rate will result in an impact force that can be partially, or fully, absorbed by the plunger itself.

It should be noted that although the hardware aspects of the of the present invention have been described with reference to the exemplary embodiment above, other alternate embodiments of the present invention could be easily employed by one skilled in the art to accomplish the internal shock absorber aspect of the present invention. For example, it will be understood that additions, deletions, and changes may be made to the internal shock absorber plunger with respect to design, shock absorber mechanisms (such as spring types etc.), plungers with bypass functions, geometric designs other than those described above (snake plungers etc.), and various internal part designs contained therein.

Although the present invention has been described with reference to preferred embodiments, numerous modifications and variations can be made and still the result will come within the scope of the invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. 

1. A plunger comprising: a cylindrical body having an upper and a lower end; at least one end having a connecting member to connect thereto a shock absorbing assembly; said shock absorbing assembly comprising: a moveable piston; a cylinder wall housing the moveable piston; an internal shock absorbing element located between the piston and an internal stop; and wherein a falling or a rising of the plunger results in the plunger hitting a well stop, causing the internal shock absorbing element to absorb a portion of an impact force created by the plunger striking the stop.
 2. The plunger of claim 1, wherein the cylinder body connecting member is a threaded male member, and the shock absorbing assembly has a receiving female member.
 3. The plunger of claim 1, wherein the shock absorbing assembly further comprises a cylindrical case housing which receives a cap which in turn supports the internal shock absorbing element against the internal stop via a lock nut which in turn supports the piston inside the case housing.
 4. The plunger of claim 3, wherein the internal shock absorbing element further comprises an elastomeric block.
 5. The plunger of claim 3, wherein the internal shock absorbing element further comprises a spring.
 6. The plunger of claim 3, wherein the internal stop is formed by an internal narrowing of a hollow case housing.
 7. The plunger of claim 1, wherein the shock absorbing assembly further comprises a hollow case housing having a lower ledge to support an upper flange of a piston, where the piston extends below the lower ledge, and wherein a shock absorbing element is supported by a top of the piston inside the case housing, wherein a threaded cap secures the shock absorbing element against the top of the piston, and wherein the threaded cap has a threaded connector to mate to the connecting member of the plunger.
 8. The plunger of claim 7, wherein the threaded cap threaded connector is a female hole, and the plunger connecting member is a threaded male member.
 9. The plunger of claim 7, wherein the shock absorbing element further comprises an elastomeric body.
 10. The plunger of claim 7, wherein the shock absorbing element further comprises a spring.
 11. The plunger of claim 1, wherein the at least one end having a connecting member comprises two ends, and wherein a top end further comprises a shock absorbing assembly comprising: a moveable piston; a cylinder wall housing the moveable piston; an internal shock absorbing element located between the piston and an internal stop; and wherein a falling or a rising of the plunger to hit an external well stop results in the internal shock absorbing element absorbing a portion of an impact force created by the plunger striking the stop.
 12. The plunger of claim 11, wherein the piston further comprises an external end having a fishing neck design.
 13. A plunger comprising: a cylindrical body having an upper and a lower end; at least one end having a connecting member to connect thereto an internal shock absorber means functioning to damp a force from a plunger's impact with an external well stop; and said internal shock absorbing means further comprising a case housing having a moveable piston means therein functioning to allow an external end of the piston to impact the external well stop, and thereby impact an internal shock absorbing means functioning to deform and absorb energy.
 14. An internal shock absorber for a plunger, said internal shock absorber comprising: attachment means to a plunger functioning to allow a connection to an end of a plunger; a case housing means functioning as a cylinder housing for a piston which has an end protruding from the case housing means; and a shock absorbing means contacting the piston inside the case housing means and functioning to deform upon impact to absorb energy.
 15. A plunger comprising: an elongate body having an upper end, a lower end and a central assembly; said upper end further comprising an upper end piston which slides inside the central assembly; said lower end further comprising a lower end piston which slides inside the central assembly; said central assembly further comprising a cylindrical housing supporting an internal shock absorbing element located between the upper end and the lower end piston; and wherein a falling or a rising of the plunger results in the plunger hitting a well stop causing the internal shock absorbing element to absorb a portion of an impact force created by the plunger striking the stop.
 16. The plunger of claim 15, wherein the internal shock absorbing element further comprises an elastomeric block sandwiched between the upper end and the lower end piston.
 17. The plunger of claim 15, wherein the internal shock absorbing element further comprises a spring sandwiched between the upper end and the lower end piston.
 18. The plunger of claim 15, wherein the central assembly further comprises a cylindrical housing having an upper and a lower threaded end, each piston has a male threaded end at the central assembly, each piston having a captive nut which threads into the cylindrical housing, and wherein a seal nut captures the respective male threaded end of each piston inside the cylindrical housing.
 19. The plunger of claim 15, wherein the upper end piston further comprises a fishing neck design.
 20. A plunger comprising: an elongate body having an upper end, a lower end and a central assembly means; said upper end further comprising an upper end piston which slides inside the central assembly means; said lower end further comprising a lower end piston which slides inside the central assembly means; said central assembly means functioning to support an internal shock absorbing element located between the upper end and the lower end piston; and wherein a falling or a rising of the plunger results in the plunger hitting well stop causing the internal shock absorbing element to absorb a portion of an impact force created by the plunger striking the stop. 